def frequency_unit_conversion(frequency, current_unit: str, target_unit: str):
    """
        频率单位转换
    """
    frequency = float(frequency)
    if current_unit == target_unit:
        return round(frequency, 4)
    units = {'Hz': 1, 'kHz': 1e3, 'MHz': 1e6, 'GHz': 1e9}
    return round(frequency * units[current_unit] / units[target_unit], 4)